To control remotely household electronic appliances such as air conditioners, televisions or the like, infrared communication (IR communication) is generally used, whereby a remote control transmitter transmits an infrared control signal (IR signal) of infrared rays to the household appliances. In an IR communication system used in a home, an appropriate pulse modulation method is employed to carry IR signal control data from the remote control transmitter. For example, with a pulse width modulation (PWM) method, according to the control data for the device to be controlled, PWM modulation signals of differing pulse widths are modulated corresponding to the value of bit data thereof, and in order to prevent interference from other devices and mistaken operation, an IR signal created by secondarily modulating the PWM modulated signal with a 38 kHz carrier modulation wave is transmitted to the household appliances and other devices to be controlled.
At a controlled device, the IR signal is opto-electrically converted by a light-receiving element, passed through a bandpass filter that passes the 38 kHz signal, and the envelope of the signal output therefrom is waveform-shaped and then demodulated into the PWM modulated signal. A device-side microcomputer of the controlled device is provided with a PWM input port for receiving the PWM modulated signal. The device-side microcomputer demodulates the control data from the PWM modulated signal, and operates the various portions of the controlled device according to the control data.
In remote control implemented with this IR communication system, due to the blocking of IR signals by shielding material interposed between the remote control transmitter and the controlled device or due to the limited angle of directivity of a light-emitting element that emits the IR signal, the IR signal may not reach the light-receiving element unless the IR signal is precisely emitted in the direction toward the light-receiving element of the controlled device. With larger screen televisions, for example, the display size of which has been increasing in recent years, as a result of design restrictions, the location at which the light-receiving element is installed is often not obvious, and a problem occurs in which an IR signal is transmitted toward a different location and the device to be controlled does not respond to the remote control transmitter.
Thus, attention is being drawn to a wireless RF (radio frequency) wave communication (RF communication) system for carrying RF signals without restriction on the direction of transmission and that enables transmission even when shielding material is interposed. In a RF communication system, for example, a 2.4 GHz band RF signal modulated with control data from the remote control transmitter is transmitted from an antenna, and the RF signal is received by an antenna at an RF reception circuit unit at the controlled device and passed through a bandpass filter, so that only the 2.4 GHz band RF signal is input. The control data is then demodulated from the RF signal. The demodulated control data is outputted to a device-side microcomputer of the controlled device, and the device-side microcomputer operates the various portions of the controlled device according to the control data.
Many existing household appliances (i.e., controlled devices) are controlled by a remote control transmitter with an IR communication system. In a known RF communication system as disclosed in Japanese Unexamined Patent Application Publication No. 2004-31999, which is incorporated by reference herein in its entirety, a wireless/infrared adapter that converts RF signals into IR signals is interposed to enable even an IR signal-controlled device to be controlled remotely with a remote control transmitter that transmits RF signals.
A conventional RF communication system 100 in which a wireless/infrared adapter is interposed is described with reference to FIG. 7. In this figure, reference numerals 101a and 101b indicate a PC (personal computer) and PDA (personal digital assistant), respectively, each constituting a remote control transmitter 100 capable of transmitting and receiving control data, and RF signals transmitted from these remote control transmitters 101 are received at an antenna 104a of a wireless transceiver unit 104 provided on a wireless/infrared adapter 103. A conversion unit 105 of a wireless/infrared adapter 103 demodulates the control data from the RF signal, converts the demodulated control data into a pulse modulated signal that can be demodulated by the controlled devices 107, e.g. a TV 107a, a VCR 107b and so on, and then outputs [the pulse modulated signal] to an infrared transceiver unit 106. The infrared transceiver unit 106 outputs a pulse modulated IR signal, having been pulse modulated with the control signal, to the controlled devices 107.
Accordingly, with the conventional RF communication system 100, the positioning of the wireless/infrared adapter 103 that transmits IR signals in the vicinity of controlled devices 107 that are not blocked by a shielding material enables existing IR communication system-controlled devices 107 to be controlled remotely with the remote control transmitter 101 that transmits RF signals, without consideration of the existence of shielding material or the transmitting direction of the remote control transmitter 101.
A remote control transmitter as disclosed in Japanese Unexamined Patent Application Publication No. 2006-522556, which is incorporated by reference herein in its entirety, is capable of transmitting and receiving either IR signals or RF signals, and capable of controlling remotely either an existing IR communication system-controlled device or a RF system-controlled device. A RF communication system as disclosed in Japanese Unexamined Patent Application Publication No. 2001-169368, which is incorporated by reference herein in its entirety, includes a RF reception circuit unit for receiving RF signals that is added to an existing IR communication system-controlled device thereby also enabling the device to be controlled remotely with a RF communication system.
The conventional RF communication system 100 as illustrated by FIG. 7 requires that a wireless/infrared adapter 103 be positioned between the controlled device and the transmitter. However, positioning of the RF communication system 100 between the controlled device and the transmitter at a location free from any shielding material that does not obstruct movement within a home is extremely difficult, and may be aesthetically impractical.
Moreover, the RF signal reception is in a hot standby state, and the large quantity of electric power consumed during standby quickly drains an internal battery and necessitates the use of a power supply cable to supply electric power. The wiring of a power supply cable within a home, however, creates a problem of additional complexity.
In the remote control transmitter capable of transmitting and receiving either IR signals or RF signals cited in Japanese Unexamined Patent Application Publication No. 2006-522556, an existing IR communication system-controlled device can be controlled remotely, but in the transmission and reception of signals to and from an existing IR signal-controlled device, the problem arising from an IR communication system, whereby the device cannot be controlled due to the direction of IR signal transmission or the existence of shielding material, is present as before.
Additionally, in the RF communication system as disclosed in Japanese Unexamined Patent Application Publication No. 2001-169368 in which a RF reception circuit unit for receiving RF signals is added to an existing IR communication system-controlled device, there is a problem whereby the mere addition of a RF reception circuit unit does not enable the output thereof to be connected to a device-side microcomputer of the controlled device. Namely, the RF communication system uses serial communication, and the control data output from the RF reception circuit unit is bit stream data. Therefore, a universal asynchronous receiver transmitter (UART) for converting the serial bit stream into parallel byte-data used by the device-side microcomputer must be interposed between the RF reception circuit and the device-side microcomputer.
Moreover, the device-side microcomputer mounted on the controlled device is often an IC chip developed specifically for an IR communication system, and in response to requests for lower cost, is provided only with a pulse modulated signal input port, such as a PWM input port. When using a RF communication system to control a controlled device equipped with this type of device-side microcomputer, the addition of only a RF reception circuit unit having an antenna and a UART interface is insufficient, and an extensive modification is required in which the entire chip, including the device-side microcomputer, is replaced.